Symbol readers, such as barcode scanners and readers, are well known in the art. Often, such devices are based upon charge coupled device (CCD) technology, wherein a linear array CCD device is used to recover light reflected from the barcode. In such systems, plural LEDs are used as a light source to illuminate an object such as a barcode. The reflected light is received by the CCD linear array, which converts the light energy into electrical energy. The varying electrical signal can then be processed to recover the barcode symbol, which represents the information of interest.
In such systems, the light source often must be calibrated with manual adjustments because of variances between power output by the individual LEDs, total LED output, sensitivities of the CCD, and other variances among such systems. This calibration is often accomplished in the prior art by physically adjusting a variable resistor, thereby altering the amount of current supplied to the LEDs, and hence, changing its brightness.
Although this practice is relatively straightforward and well known in the art, it adds costs to the product. Manual adjustment is required, and the additional cost of the variable resistor to adjust the current supplied to the LEDs is not insignificant. Moreover, the requirement for an additional component, ie; the variable resistor, adds another potential point of failure in to the system, and hence further increases cost. Accordingly, the prior art systems are less than optimal in the sense that costly procedures and components are required in order to appropriately calibrate and adjust the light source(s) used to illuminate the barcode or similar image.